The minimum period problem in cataclysmic variables

Abstract

We investigate whether consequential angular momentum losses or an intrinsic deformation of the donor star in cataclysmic variables (CVs) could increase the CV bounce period from the canonical theoretical value ∼65 min to the observed value Pmin ≈ 77 min, and whether a variation of these effects in a CV population could wash out the theoretically predicted accumulation of systems near the minimum period (the period spike). We are able to construct suitably mixed CV model populations that a statistical test cannot rule out as the parent population of the observed CV sample. However, the good quality of the fit is never convincing, and is always slightly worse than for a simple, flat period distribution. Generally, the quality of the fit is much improved if all CVs are assumed to form at long orbital periods. The weighting suggested by King, Schenker and Hameury does not constitute an improvement if a realistically shaped input period distribution is used.